Northern California fish feared extinct due to drought still hanging on in small isolated creek

With a fish net in one hand and backpack in the other, UC Davis fish biologist Peter Moyle set out across the dry Sierra foothills Thursday to look for a fish he feared was destined for extinction because of drought.

What he found puzzled him.

On a dry hill, with the sun blazing, he came across a thriving creek – with plenty of water and fish.

The fish in question is the Red Hills roach, which is found only in the creeks and pools amid the serpentine rock-lined hills south of Highway 120, west of the town of Sonora.

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Because of the intense drought, Moyle feared that most of the creeks and pools the fish thrive in were now just rocky bottoms. “We were pessimistic we would even find anything,” said Moyle. “So we brought buckets and an ice chest with an aerator in it to take fish back.”

Whatever fish he could find he planned to bring back to UC Davis.

If none was found, it would have been the first fish extinction in California since the High Rock Spring tui chub disappeared in 1989.

Experts say climate change will eventually threaten many fish species in California. In a study he co-authored recently, Moyle estimated that 82 percent of California’s 129 native fish species have been deemed highly likely to dwindle in number or go extinct over the next century.

For the Red Hills roach, it may not take more than another year of drought to trigger extinction, given that most of its habitat has dried up. The Six Bit Gulch creek where the fish are known to thrive was nothing more than a sea of jagged rock this week.

But nearby at Horton’s Creek, Moyle found a rare green oasis. Wild sunflowers and other weeds were growing robustly, and the water held more than 200 Red Hills roach fish.

“This was a total surprise to me,” said Moyle. “Right now there seems to be plenty of water, and the fact that the spring is still working is amazing.”

There were so many of the fish in the 400-foot-long creek that Moyle and UC Davis post-doctoral researcher Rebecca Quiñones did not see cause to trap and rescue them.

Moyle said he believes the aquifer there lies close to the surface and the water is seeping into the stream from the ground both above and below the creek.

The continued survival of the Red Hills roach was a small bit of good news in what has been a bad news year for a state thirsty for water.

With drought in its third year, Quiñones said, “We’re starting to see declining (fish) populations and declining community structures, and less diversity in our streams. And that’s a concern for long term conservation of our native fishes.”

Moyle said he believes the drought may rob the state of a natural heritage. He noted that most of the fish extinctions in California have occurred since the 1960s.

“Eighty percent of the fish in California are found only in California,” said Moyle. “This is our problem. These fish are part of out heritage.”

The Red Hills roach is a small species, never more than 4 inches long. At Horton Creek, most were young and about an inch long.

Brownish with a yellow belly, the Red Hills roach is skittish and prefers shallow streams. It is a wonder of adaptation to a harsh environment. It thrives in water that would kill many other fish. The water in the Red Hills region is filled with naturally occurring heavy metals such as magnesium.

It can live in water temperatures that reach as high as 100 degrees, Moyle said. “This fish can tell us a lot about how fish survive in very difficult conditions.”

He said he believes that a continuing drought may imperil the 200 fish remaining in Horton Creek. “This species is completely isolated here, so what happens here will determine their fate,” Moyle said.

In non-drought years, the fish would be thriving in a half dozen streams that dot the Red Hills area. An inventory of 15 streams and pools on Thursday found half completely dry and the rest almost dry. Of those that held any water, Horton Creek was the only one with Red Hills roach in it. However, the creek is showing signs of drought stress, since it is now only half its normal size, said Moyle.

Moyle said he plans to return in September to assess the Red Hills roach population again. “If this stream flow holds up through the end of this season, I think this fish will survive.”